Auto merge of #424 - ptrv:ycmd-eldoc-recommended-setup, r=abingham
Auto merge of #424 - ptrv:ycmd-eldoc-recommended-setup, r=abingham

Use recommended way to setup eldoc-documentation-function

Since we our minimum supported Emacs version is 24.4 we can now just use the recommended way to setup `eldoc-documentation-function` with `add-function` from `nadvice` package.

emacsmirror/ycmd,ptrv/emacs-ycmd,phst/emacs-ycmd,abingham/emacs-ycmd,phst/emacs-ycmd,emacsmirror/ycmd,abingham/emacs-ycmd,ptrv/emacs-ycmd,abingham/emacs-ycmd,emacsmirror/ycmd,emacsmirror/ycmd,phst/emacs-ycmd,ptrv/emacs-ycmd,phst/emacs-ycmd,abingham/emacs-ycmd,abingham/emacs-ycmd,abingham/emacs-ycmd,ptrv/emacs-ycmd,ptrv/emacs-ycmd,emacsmirror/ycmd,ptrv/emacs-ycmd,phst/emacs-ycmd,emacsmirror/ycmd,phst/emacs-ycmd